Note: Descriptions are shown in the official language in which they were submitted.
CA 02450042 2003-12-08
WO 02/102199 PCT/US02/18787
IMPROVED ERGONOMIC CHAIR
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates generally to a chair of the type suitable for
use in an
office environment and, more particularly, to a reclining office chair having
several
structural and o.perating features which offer a number of ergonomic and other
advantages over the prior art.
Description of the Related Art
Over many years attempts have been made to design chairs for use in office
environments which are comfortable to use and thereby avoid user fatigue over
prolonged use. In one simple form a chair may be provided with a swivel base
for ease
of turning aild include a control mechanism which permits the chair to rock. A
disadvantage of these relatively simple chairs is that conjoint rocking motion
of the chair
seat and back naturally lifts the user's feet off the floor, which can create
stability
problems and place upward force on the front of the user's thighs whicli can
reduce fluid
circulation in the user's legs.
To iinprove on the foregoing chair construction, chair controls are known
which
provide for synchronous movement of the chair seat and back. Where office
chairs are
concerned, a "synchronous control" means the arrangement of a combined or
dependent
back adjustinent and seat adjustment, that is to say the adjustment of the
back inclination
fiuida.inentally also results in an adjustment of the sitting surface. An
example of a
synchronous chair control is disclosed in U.S. Patent No. 5,31 8,345, issued
to Olson and
assigned to the common assignee herein. With the aforementioned Olson control,
the
chair back is designed to tilt at one predetermined rate of recline while the
seat tilts
synchronously at a much lesser rate. The result is that the user's feet are
not lifted from
the floor when the back is reclined. Also, fluid circulation in the user's
legs is not
interrupted by substantial upward-movement of the forward end of the seat,
Another
advantage of this control is that undesirable "shirt pull" is minimized by the
strategic
location of the tilt axis. Other examples of synchronous chair controls are
disclosed in
U.S. Patent Nos. 5,366,274 and 5,860,701, to name a few.
In U.S. 6,125,521, it is disclosed to be desirable to provide a chair having a
seat
and backrest which pivot generally about the axis of the hip joints of the
user. A
disadvantage of that chair is that as the chair back reclines, the rear of the
seat also tilts
downwardly, having the effect of changing the user's gaze angle. Further, in
that chair,
CA 02450042 2003-12-08
WO 02/102199 PCT/US02/18787
-2-
the arms also tilt with the chair back, thus displacing the user's arms away
from any work
surface. In U.S. 5,979,984, the seat is arranged to both slide forwardly and
the rear
portion of the seat moves downwardly as the back reclines.
Another feature embodied in recently designed office chairs that offers
considerable ergonomic advantages is a tilt limiter feature for the chair
back. With such
a mechanism built into the chair control, the user may selectively set the
degree of back
recline at a predetermined angle thereby adding to comfort as the chair is
used. An
example of such a tilt limiter mechanism is disclosed in U.S. Patent No.
6,102,477 issued
to Kurtz and assigned to the common assignee herein. This particular mechanism
offers
the advantage of providing for infinitely variable angles of tilt within a
predetennined
overall range. The mechanism is also highly cost-effective to construct.
Yet another feature of current ergonomically designed chairs is the provision
of
height and pivot adjustable arm pads. Such a feature is particularly
advantageous in
providing the user with additional support to the arms, forearms, wrists and
shoulders in
order to minimize repetitive stress injuries when the user is keyboarding, for
example,
while seated in the chair. An example of such an adjustable arm pad using a
gas cylinder
is disclosed in U.S. Patent No. 5,908,221 issued to Neil.
Yet another feature of current ergonomically designed office chairs includes
an
adjustable luinbar support mechanism for providing preselected chair back
tension in the
region of the user's lower back. An adjustable lumbar support allows the chair
user to
select a comfortable level of pressure on the lower back depending upon the
specific
office task being performed. Such a mechanism is disclosed, for example, in
U.S. Patent
No. 5,797,652.
Still another feature of certain ergonomically designed office chairs,
particularly
of recent viiltage, is the incorporation of fabric mesh into the construction
of the chair
seat, and/or back. These materials ostensibly offer the advantage of enhanced
air
circulation for and consequent heat transfer from the chair user's body, which
can
improve the comfort of the chair. An example of the use of such fabric mesh in
an office
chair is disclosed in aforementioned U.S. Patent No. 6,125,521 issued to
Stumpf et al.
Yet another feature of certain ergonomically designed chairs is the provision
of a
seat cushion having the capability of effecting heat transfer from the chair
user's buttocks
area while at the same time offering comfort to the user while seated,
together with
adequate support. Known seat cushions having such capability may involve a
passive or
CA 02450042 2007-08-20
-3-
active air flow circulation feature of the type disclosed, for example, in U.
S. Patent No.
6,179,706.
SUMMARY OF THE INVENTION
The present invention provides a totally redesigned ergonomic chair that
incorporates simple but improved functional and esthetic aspects in all areas
of a
modular chair construction and in its use, including synchronous tilt of back
and seat; tilt
limit control; separate seat adjustment; arm adjustment; adjustable lumbar
support;
cushion airflow; mesh attachment and modular base frame assembly.
The various subfeatures of these various components are the subject of the
following individual applications, all commonly assigned:
Multi-position Tilt Limiting Mechanism
U. S. Patent No. 6,616,231, issued September 9, 2003
Locking Device for Chair Seat Horizontal Adjustment Mechanism
U. S. Patent No. 6,688,692, issued February 10, 2004
Adjustable Chair Seat Locking Mechanism
U.S. Patent No. 6,634,711, issued October 21, 2003
Height and Pivot-Adjustable Chair Arm
U. S. Patent No. 6,702,386, issued March 9, 2004
Vertically and Horizontally Adjustable Chair Armrest
U.S. Patent No. 6,773,072, issued August 10, 2004
Lumbar Support for a Chair
U. S. Patent No. 6,572,190, issued June 3, 2003
Body Support Member
U. S. Patent No. 6,598,251, issued July 29, 2003
Chair Back Construction
U. S. Patent No. 7,014,269, issued March 21, 2006
Chair Back Construction
U.S. Patent No. 6,729,696 issued May 4, 2004
Chair of Modular Construction
U. S. Patent No. 6,568,760, issued May 27, 2003
CA 02450042 2003-12-08
WO 02/102199 PCT/US02/18787
-4-
In each of these cases, features combine to provide an overall chair that is a
significant improvement over the prior art.
Thus, for example, the present invention provides a reclining chair having a
four
bar linkage system that causes the rear of the seat to elevate as the back is
reclined
lendiiig an unusual and comfortable balance during reclining. A very simple
and
econoinically constructed tilt liinit control conveniently and effectively
limits the degree
of chair back tilt to one of several reclined positions by manual movement of
a lever.
Horizontal positioning of the chair seat cushion may be accomplished using a
simple but
positive locking device that allows the chair user to select a preferred
horizontal seat
cushion position. Height and pivot adjustable chair arms are simply and
positively
actuated with the push of a button or simple rotation, lending convenient
adjustment to
suit a specific work task. A lumbar support is easily height adjustable, by
providing
tension to the back frame and requires no screws or adjustment knobs in its
adjustment
mechanism, and also does so by avoiding direct contact of the lumbar support
with the
back of the user. A modular cushion seat includes a comfortable thermal air
flow layer
and gel layer which is vented uniquely for air circulation and stress and
pressure
management. The back of the chair is of fabric mesh construction and includes
a novel
attachment system for superior comfort. The base and baclc of the chair are of
modular
construction that provides for ease of assembly and lends rigidity to the
chair
construction, and in which an open skeletal frame structure displays both the
simplicity
of the chair structure while adding to its esthetic appeal.
A primary object of the present invention is a tiltable chair wherein users of
substantially all weights and sizes may be continuously balanced in the chair
at any
selected reclination position, therefore enhancing both "fit" and "comfort."
The present
invention improves over the prior art by providing an ergonomic chair having a
four-bar
linkage arrangement wherein a-lower frame member is provided with a rigid
front
support and a rigid rear support. with a seat member pivotably connected to
the front
support. A back rest has a first pivot point connected at an upper end of the
rear support
of the lower frame meinber. A link meinber pivotably connects at a first end
to a rear
support of the seat member and at a second end to a second, lower pivot point
on the
back rest. This novel arrangement permits tilting movement of the backrest
rearwardly
relative to the lower frame member wliile concurrently causing elevation of a
rear
portion of the seat member, pennitting the feet to remain on the floor and
alleviating
pressure on the user's thighs. This is accomplished by a linkage mechanism
creating an
instantaneous center of rotation of the chair seat and back that is
approximately at the
CA 02450042 2003-12-08
WO 02/102199 PCT/US02/18787
-5-
user's hip, so that the movement of the seat and back reduces undesirable
"shirt pull."
This arrangement also is more responsive to the user and provides correct back
support
throughout tilt.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other novel features and advantages of the invention will be
better understood upon a reading of the following detailed description taken
in
conjunction with the accompanying drawings wherein:
FIG. 1 is a left front perspective view of an ergonomic chair constructed in
accordance with the principles of the invention and incorporating all of the
improved
modular components;
FIG. 2 is an exploded perspective view thereof;
FIG. 3 is an exploded perspective view providing more details of the central
support module of the present invention;
FIG. 4a is a left side view of the assembled chair of FIG. 1;
FIG. 4b is a right side view of the assembled chair of FIG. 1;
FIG. 5 is a front view thereof;
FIG. 6 is a rear view thereof;
FIG. 7 is a top view thereof;
FIG. 7a is a partial top view of the chair seat witll the cushion assembly
removed;
FIG. 8 is a bottom view of the assembled chair of FIG. l;
FIG. 9 is a bottom view with the chair base removed;
FIG. 10 is a partial left side view illustrating the chair in a fully upright
position;
FIG. 10a is a side schematic view showing the preferred dimensional
relationships between the chair components with the chair back in a fully
upright
position;
CA 02450042 2003-12-08
WO 02/102199 PCT/US02/18787
-6-
FIG. 11 is a partial left side view of the chair shown in a partially reclined
position;
FIG. 12 is a partial left side view of the chair shown in a fully reclined
position;
FIG. 12a is a side schematic view showing the preferred dimensional
relationships between the chair components when the chair back is in a fully
reclined
position;
FIG. 13 is a side schematic view showing the linkage arrangement of the chair;
FIG. 14 is a side schematic view showing the kinematics of the chair;
FIG. 15 is a perspective view of the preferred chair back assembly of the
present
invention;
FIG. 16a is an exploded perspective view of the preferred chair back assembly
of
the present invention;
FIG. 16b is a perspective view of the assembled back frame without the
backrest
thereon;
FIG. 17 is a perspective view of the chair back assembly illustrating the
adjustability of the preferred form of adjustable lumbar support;
FIG. 18 is a cross-sectional view taken substantially along the line 18-18 in
FIG. 15;
FIG. 19 is an enlarged view of the circled section in FIG. 18;
FIG. 20 is a partial cross sectional view showing the relationship of the
lumbar
member of the mesh carrier taken substantially along the line 20-20 in FIG.
15;
FIG. 21 a is an enlarged view of one form of mesh arrangement for use in the
invention;
FIG. 21b is an enlarged front view of a second preferred embodiment of mesh
arrangement for use with the present invention;
FIG. 21c is an enlarged rear view of the mesh of FIG. 21b;
CA 02450042 2003-12-08
WO 02/102199 PCT/US02/18787
-7-
FIG. 22 is an enlarged exploded view showing one form of assembly of the mesh
to a carrier;
FIG. 23 is a view similar to FIG. 22 showing an adhesive bonding method of
fastening the mesh to a carrier;
FIG. 24 is an enlarged partial sectional view showing the carrier mounted to
the
top of the back frame;
FIG. 25 is an enlarged partial sectional view showing the carrier mounted to
the
bottom of the back frame;
FIG. 26 is an enlarged partial bottom view showing some detail of the tilt
limit
mechanism, with the base, arms and seat removed for ease of understanding;
FIG. 26a is a cross-sectional view taken along the lines 26a-26a in FIG. 26,
showing details of the link and tilt limit meclianism with greater clarity;
FIG. 27 is a bottom exploded perspective view showing further detail of the
tilt
limit mechanism;
FIG. 28 is an enlarged perspective view of the stop plate of the tilt limit
mechanism;
FIG. 29 is a top perspective view of the seat plate;
FIG. 30 is a cross-sectional view of the seat plate taken along the line 30-30
in
FIG. 29;
FIG. 31a is an exploded perspective view looking up into the assembled seat
plate and seat pan;
FIG. 3 lb is an exploded perspective view looking down on the assembly of the
seat pan and seat plate;
FIG. 32 is an exploded perspective view of a preferred seat cushion assembly
of
the present invention;
FIG. 33 is a front view of a preferred form of arm assembly for use with the
present invention;
CA 02450042 2003-12-08
WO 02/102199 PCT/US02/18787
-8-
FIG. 34 is a cross-sectional view of the preferred arm assembly taken along
the
line
34-34 in FIG. 33;
FIG. 35 is an exploded sectional view of the portion of the arm assembly as
illustrated in the dashed circle portion of FIG. 34, with the armrest in a
locked position;
FIG. 36 is an elevation view of a guide tube;
FIG. 37 is a plan sectional view taken along line 37-37 of FIG. 36;
FIG. 38 is an elevation sectional view taken along lines 38-38 of FIG. 36;
FIG. 39 is a plan sectional view taken along line 39-39 of FIG. 36;
FIG. 40 is an enlarged exploded isometric view of the top of the guide tube
and
an activator nut;
FIG. 41 is an enlarged elevation view of a rod;
FIG. 42 is a downward looking isometric view of an armrest base;
FIG. 43 is an upward looking isometric view of the armrest base;
FIG. 44 is a sectional elevation view taken along line 44-44 of FIG. 42;
FIG. 45 is a top plan view of a cap;
FIG. 46 is an elevation view of the cap;
FIG. 47 is a bottom plan view of the cap;
FIG. 48 is an enlarged isometric view of a lever;
FIG. 49 is a plan sectional view taken along line 49-49 of FIG. 33 showing the
armrest in a locked position;
FIG. 50 is a view similar to that shown in FIG. 49 except that the annrest is
shown in an unlocked position.
CA 02450042 2007-08-20
-9-
FIG. 51 is a left front perspective view of another ergonomic chair
constructed in
accordance with the principles of the invention and incorporating all of the
improved
modular components.
FIG. 52 is a right front perspective view of the chair shown in FIG. 51.
FIG. 52a is an exploded perspective view of the chair shown in FIG. 51.
FIG. 53 is a right side view of the chair shown in FIG. 51.
FIG. 54 is a left side view of the chair shown in FIG. 51.
FIG. 55 is a front view of the chair shown in FIG. 51.
FIG. 56 is a rear view of the chair shown in FIG. 51.
FIG. 57 is a top view of the chair shown in FIG. 51.
FIG. 58 is a bottom view of the chair shown in FIG. 51.
FIG. 59 is a bottom view as shown in FIG. 58 with the chair base removed.
FIG. 59a is a partial top view of the chair seat of the chair shown in FIG. 51
with
the cushion removed.
FIG. 60 is a partial left side view illustrating the chair shown in FIG. 51 in
a fully
upright position.
FIG. 60a is a side schematic view of the chair illustrated in FIG. 51 showing
the
preferred dimensional relationships between the chair components with the
chair back in
a fully upright position.
FIG. 61 is a partial left side view of the chair illustrated in FIG. 51 shown
in a
partially reclined position.
FIG. 62 is a partial left side view of the chair illustrated in FIG. 51 shown
in a
fully reclined position.
FIG. 62a is a side schematic view of the chair illustrated in FIG. 51 showing
the
preferred dimensional relationships between the chair components when the
chair back is
in a fully reclined position.
CA 02450042 2007-08-20
-10-
FIG. 63 is a side schematic view of the chair illustrated in FIG. 51 showing
the
linkage arrangement of the chair.
FIG. 64 is a side schematic view of the chair illustrated in FIG. 51 showing
the
kinematics of the chair.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, and initially to FIGS. 1 and 2, an improved
ergonomic chair constructed in accordance with the numerous principles of the
invention
is shown and designated generally by the reference numeral 10. The chair 10
comprises
as its principal components a back 20 and seat 30. Suitable armrest assemblies
40 having
upper armrest pads 408 may be provided. The chair 10, in a conventional
manner, may
be supported on a spider base 15 movable on casters 16.
As shown in FIGS. 10-12, the chair 10 is so constructed as to have synchronous
movement of the back 20 and seat 30. The modular chair construction generally
is
described in greater detail in aforesaid U.S. Patent No. 6,568,760. The chair
10 receives
the upper end of a gas cylinder 17. The gas cylinder 17 is preferably a two-
stage type
available from Stabilus GmbH of Germany. This cylinder 17 is operable by a
manually
pivotable lever arm 18 which activates the cylinder 17 for height and
adjustability of the
chair 10 in a manner well-known in the art, the advantage in this case is that
movement
of the arm 18 in either up or down direction effects movement of the cylinder
to either
direction.
For purposes of clarity of discussion only, the chair 10 will be described and
claimed with reference to up, down, left and right and forward and rear as
though a user
were seated on the chair, but without intent to limit the claims except where
apparent.
Further, because many of the parts are identical but are mirror images in
arrangement,
the same part number will be used to describe like parts but with an "L" or
"R"
designation for the left or right side used only as and when necessary.
The chair 10 is formed of modular construction. It has a central base or
support
module 100 (FIG. 3). The module 100 has a mounting section 101 extending
transversely. The mounting section 101 forms a support which receives
elongated seat
and back frame support members 110. Armrest modules or assemblies 40 are
attached at
the ends of the central base member 100 by bolts and hidden nuts (not shown).
The lower
curved end portion 402 of each of the arm rest modules 40 is positioned on the
CA 02450042 2003-12-08
WO 02/102199 PCT/US02/18787
-11-
mounting section 101 and extends past each end of the first and second
elongated seat
and back support modules 110.
The armrest modules 40 have upper end portions 401 to which armrests 408 may
be attached, as hereinafter described.
FIG. 3 is a front view of the central base module 100 illustrating the top 102
and
bottom 103 thereof as well as the opposing ends 104 thereof. At the bottom
wal1103 is a
hub 105 for securing the central base to the top of a hub for the
piston/cylinder
arrangement 17.
Each elongated seat and back frame support member 110 has a front seat member
support end 130 and a rear backrest frame support end 120. As can be observed,
the rear
ends 120 are separated at a greater lateral distance then the front ends 130.
Each end
120 and 130 has an aperture 121 and 131, respectively, therethrough for
receiving
appropriate pivot pins (not shown).
As can be best seen in FIGS. 2a, 6, 10 and 16a, a backrest module or assembly
200 which is a skeletal frame in arrangement, comprises a generally splayed
outwardly
U-shaped frame formed of a pair of spaced uprights 201 and having a lower
connecting
bight segment 206 (FIG. 9). An upper transverse member 207 and a lower
transverse
member 208 are both fixedly connected to uprights 201 to provide rigidity
thereto. The
lower member 208 is affixed to each upright 201 by an appropriate "C" shaped
member
209 held in position by threaded fastener 202 fed into threaded bosses 203 one
each
upright 201. The meinbers 209 serve to space the lower transverse member 208
forwardly of the uprights 201 for reasons which will be apparent. The lower
transverse
member 208 and the upper end assembly 205 of the uprights 201 receive and
support a
carrier 220 in which a mesh fabric 290 is positioned. The uprights 201 also
are
configured to support an adjustable lumbar member 250, all as described
hereafter.
The right and left outer ends 210 on lower transverse member 208 of the
backrest
assembly 200 provide pivotal attachment to the rear ends 120 of corresponding
ones of
the first and second elongated seat and back support modules 110 via pivot
pins and
bearing sleeves through apertures 121 in the support member 110 and openings
211 in
the ends 210.
Centrally positioned lower biglit portion 206 has at its forward end a clevis
arrangement 212 defined by a forwardly extending bracket 212a on which are
formed a
pair of spaced tabs 213 having openings 214 thereon for receiving a pivot pin.
The
CA 02450042 2007-08-20
-12-
forward end of the bracket 212a has a stop plate engagement member or
projection 215
thereon that cooperates with the tilt limit mechanism as hereinafter described
(see FIGS.
15 and 26).
With reference to FIGS. 29, 30, 31a and 31b, a seat member assembly or module
300 is illustrated in detail and includes generally a seat plate 330, a seat
pan 301 and a
fastener 303. Details of the seat assembly 300 are provided hereinafter and in
U.S. Patent
No. 6,634,711 referenced above.
Briefly, the assembly 300 includes the seat plate 330 having a front end 331
having pivot pin apertures 332 and a pocket or housing style rear end 333. A
pivot
attachment means such as pivot pins (not shown) passes through the openings
132 in seat
support 110 and into apertures 332 and are used to couple the forward end 331
of the seat
plate 330 to the front ends 130 of each of the respective elongated seat and
back support
members 110.
A housing type structure is provided at the rear end 333 of the seat plate
330, and
has depending outer walls 346 which include a lower bottom wall portion 347
extending
partially across the width of the seat plate 330 to define the bottom of the
housing.
Spaced inwardly from the outer walls 346 are a pair of inner walls 348,
provided with
apertures 349 therethrough for purposes of receiving pivot pins (not shown)
therethrough. A large opening 345 for receiving the clevis and projection
members 215
and is disposed between the inner walls 348. At the top of the very rear of
the seat plate
330 is a tab-like projection 350 having apertures 351 therethrough for reasons
later
explained. Positioned in a portion of the housing at the rear end 333 of the
seat plate 330
are a pair of spaced link members 216, one lower end 217 of each of which is
pivotably
attached to the lower portion of the rear seat plate via pins at apertures 349
and the other
upper end 218 of each which is attached to one tab 213 of the clevis 212 on
the back rest
frame module 200, as is described in more detail hereafter (see FIGS. 7a, 10
and 26a).
The rear end 333 of the housing section of seat plate 330 is constructed for
pivotal coupling to the clevis arrangement 212. This pivotal coupling
comprises the pair
of laterally spaced link members 216, each having the first lower end 217 for
pivotal
coupling to the respective sides of the housing structure 346 on the inside
spaced inner
walls 348 and the second upper ends 218 for pivotal coupling to the respective
sides of
the aperture/tabs 213 of the clevis.
CA 02450042 2003-12-08
WO 02/102199 PCT/US02/18787
-13-
A pivot pin (see FIG. 7a) 219 extends through the openings 214 in the tab
members 213 of the clevis, and passes through openings in the second end 218
of each of
the link members 216. The pin 219 extends into spaced and defined surface
areas 352 on
the inner walls 348 for defining movement of the links. As seen in FIG. 9A,
the upper
surface 352 of each inner wall supports the ends of pin 219 and provides the
guide path
and limit stops for movement thereof and thus of the links 216. The first or
lower end
217 of each link member 216 is pivotally connected to the bottom portion of
inner walls
348 via pins (not shown) that are passed through the apertures 349 disposed
near the
bottom wall of each spaced inner wa11348. The upper ends 218 of the links 216,
when
the chair is unweighted by a user (or if weighted but not reclined), will be
at the upper
end of the surface 351. As the back 20 reclines or tilts, the pin 219 will
move along the
surface 352 toward the bottom thereof. Because the link also is pinned to the
seat 330 at
aperture 349, it will cause the rear 333 of the seat plate 330 to rise and
rotate about front
end 331.
The relative positions of the seat 30 and back 20 of the chair 10, during
reclining
of the back 20, can be seen in the side views of FIGS. 10-12. As illustrated
in these
views, the chair seat plate 330 is pivotably connected via pins 135 at pivot
points P30 to
the forward end 130 of support members 110 (only one of which can be seen) and
is
pivotably connected at rear pivot points P32 to the lower ends 217 of the
linlcs 216 at the
aperture 349 (only one of which can be seen). Each link 216 in tuzm is
pivotably
connected at its upper end 218 at point P34 to the clevis 212 on the back
frame assembly
200. The back frame assembly 200 also is pivotably connected via member 208 at
point
P20 to the two laterally spaced end positions 120 of support members 110.
As shown in the dimensional schematic of FIG. 10a, when the chair back 20 is
in
a fully upright position the seat plate 330 (and thus the seat) in one
preferred form is
inclined to the rear and forms an angle of about 15.7 degrees from horizontal,
although
this angle can be in a range of between about 10 and 20 degrees. The preferred
distance
between pivot points P30 and P31 is about 12.889 inches and the distance
between pivot
points P31 and P34 of the liiiks 42 is approximately 2.01 inches, although
these distances
can be in ranges of between about 10 and 15 inches and about 1.5 to 2.5
inches,
respectively. Further, the preferred distance between pivot points P20 and P34
is
approximately 4.71 inches while the horizontal distance between pivot points
P30 and P2o
is about 14.5 inches. The distance between pivot points P20 and P34 may be in
the range
of between about 3 and 6 inches while the distance between pivot points P30
and P20 may
be in a range of between about 12 and 17 inches.
CA 02450042 2007-08-20
-14-
As shown in the three stages of back tilt illustrated in FIGS. 10-12, as the
back 20
reclines rearwardly, the link members 216 move in a counterclockwise direction
of
rotation causing the rear end portion of the seat plate 333 to pivot about
pins 135 and
elevate relative to its front 331. In the fully reclined position of the back
20 as shown in
the schematic of FIG. 12a the seat plate 330 (and cushion) preferably reduces
its angle of
inclination with the horizontal from about 15.7 degrees (FIG. l0a) to about
8.7 degrees
while the afore-described distances between all pivot points remains constant.
The
reduced inclination angle may be in a range of between about 6 and 10 degrees.
This
synchronous motion of the seat plate 330 and thus seat 30 and back 20 provides
for an
exceptionally comfortable reclining motion of the chair user to aid in
avoiding fatigue as
the user is performing various work-related tasks. The ride motion is achieved
by this
simple seatback-seatrest four bar mechanism, which immediately responds to a
user
exerting a back force and/or self-weight. A back force applied by the user
induces a lift
in the rear part of the seat, and vise versa, during reclining, in a
synchronic-type motion.
The chair link mechanism restores ride stability, and attains a desirable ride
quality, equally well for a wide range of users, by varying the back force
reaction in the
mechanism. The back force reaction results from users imposing their own back
force
and/or self-weight on the chair mechanism. By proportioning linkages lengths,
and
selecting the locations of the rotationally-free hinges, i.e., the pivots, the
back force
reaction is designed to vary in order to achieve balance. This continuous
force balancing
process, which characterizes the ride motion at all positions, establishes and
maintains an
equilibrated ride. As a result, the need for a user to consciously adjust a
back tilt tension
knob, to feel comfortably balanced when reclining, is replaced with this more
adaptive
and dynamic feature. By doing so, the chair design is taken one step further
toward
conformance to all users without involving them in unnecessary conscious
feature-
adjustment efforts.
The mechanism configuration determines the location of the instantaneous
center
of chair rotation. As the configuration changes as a result of changing the
sitting posture
and position, the chair design allows the locus of its instantaneous center of
rotation to
generally coincide with the user's rotation center, i.e., hip joint, at all
locations within the
ride range (FIG. 13). This feature is calibrated for equal performance to many
users,
where the instantaneous center of chair rotation is set to move along the
locus, i.e.
trajectory. By maintaining this quality in the ride, abdominal, back, and
other
musculoskeletal straining, are all eliminated in the full ride range. A more
uniform foot
reaction is maintained in the ride, therefore, enhancing the ride quality even
further.
CA 02450042 2003-12-08
WO 02/102199 PCT/US02/18787
-15-
Also, the opening of the torso-legs angle enhances fluid circulation and other
ergonomic
factors.
Shown in FIGS. 13 and 14 are scheinatic views of the synclironous seat and
back
tilt feature employing the four-bar mechanism which allows the rear of the
seat 30 to
elevate as the backrest 20 is reclined. The mechanism is designed to
immediately
respond to the users weight and provide the correct back support throughout
the range of
back reclining. This function allows for reclining of the chair 10 about an
instantaneous
center point C that, as noted, is very closely coincident with the pivot axis
of the user's
hips and avoids undesirable "shirt pull" of the user. Also, because the front
of the seat 30
is not elevated during back reclining, no additional pressure is applied to
the front
underside of the user's thighs, and also a relatively constant gaze angle is
maintained
during reclining.
To accomplish the foregoing advantages, the chair 10 schematically comprises
four basic members and four rotationally-free pivots. The basic members
include a floor
supported member 60, a seat rest 62, a linking member 64 and a backrest 66.
The floor
supported member 60 has an upwardly directed portion 68 that terminates at an
end
defining pivot point P30 to which the seat rest 62 is pivotably connected at
its forward
portion. The member 60 also has an upwardly directed portion 70 which
terininates at an
end defining pivot point P20 to whicli the backrest 66 is pivotably connected.
A lower
portion 72 of the back rest 66 is pivotably connected at point P34 to the
upper end of
linking member 64 and a downwardly extending portion 74 of the seat rest 62 is
pivotably connected at point P32 to the other lower end of the linking member
64.
The kinematics of the chair 10 are illustrated in FIG. 14. As force F is
applied on
the backrest 66, the back tilt angle (3 increases, eye location shifts
backwards an amount
OH1, and eye elevation decreases by an amount AV3. The change in back tilt
angle (3
transmits motion by way of the upper and lower back pivots P20 and P34,
respectively, to
the linking member 64. As a result of motion set in linking member 64, the
rear seat
pivot P32 moves in coordination with pivot P34 in a composite rotational and
translation
motion. As the seat rest 62 rotates about pivot P30, a lift AV2 is caused in
the rear part of
the seat rest 62 relative to its front edge AV 1 in the amount OV2-OV 1,
therefore
introducing a seat rest angle a. During back reclining an increasing portion
of the user's
weight supported by the chair is transferred from the seat support to the back
support
while the mechanical advantage of the mechanism lifting the seat support
decreases. The
user will therefore sense a static balance position in any position of recline
and will
require little effort to move to a new position.
CA 02450042 2003-12-08
WO 02/102199 PCT/US02/18787
-16-
As the user sits in the chair, a back force, F, and/or weight, W, is exerted
on the
chair mechanism and, therefore, sets it in a self-equilibrating motion, with
ride qualities
that are designed beforehand. These forces may only be balanced by a proper
back force
reaction, and by the chair reconfiguring its geometry to the level required by
the exerted
force. By doing so, the motion response parameters appearing in FIGS. 13, 14,
are
varied in known proportions and rates to achieve the ride quality. The design
ride range
subtends a backrest angle from about 90 to about 120 .
To fine-tune the ride qualify, and to provide for static overall stiffness,
the
mechanism may also be equipped with external elements, including springs. The
addition of these external devices would further calibrate the ride quality
towards its
desirable, pre-designed features, while, at the same time, maintaining all
other functional
qualities intact. Thus, in order to assist the chair linkage mechanism in
allowing the
backrest member 20 to maintain a fully upright position when the chair 10 is
not in use,
as shown in FIG. 7a one or more extension springs 75 may be connected between
pivot
shaft 219 and the rear edge portion 350 of the seat plate 330. The pivot shaft
219
essentially also defines pivot point P34 and will cause a return force to be
exerted on back
frame assembly 200 by the springs 75.
In order to relate the explanation of the schematic linlcage as described in
FIGS.
10a, 12a, 13 and 14, to the chair 10, the respective parts on the chair
correspond to the
parts as numbered on the schematic linkage
CHAIR LINKAGE SCHEMATIC
110 60 Floor support member
330 62 Seat
216 64 Link member
201 66 Backrest
130 68 Front upward member on 60
120 70 Rear upward member on 60
212 72 Lower portion of backrest 66
346, 348, 349 74 Downward portion of seat rest 62
In FIGS. 26-28, a very simple and economical seat back tilt limit control
module
150 is associated with the seat assembly 300 using a lever handle 155 attached
to the tilt
limit module for adjusting the amount of permissible tilt of the seat back 20.
As can be
CA 02450042 2007-08-20
-17-
seen in FIG. 27, the seat plate 330 has a threaded stub 152 on the bottom side
335 thereof
to which a stop plate 154 and the lever handle 155 can be attached by a
shoulder bolt and
washer 156 that is threadedly inserted into stub through aligned orifices 157
in the
handle, stop plate and stub. The lever handle 155 may be attached to the stop
plate 154
from either side of the chair 10, and herein is shown on the left side. It
will be noted that
stop plate 154 has an outer edge 158 with a series of steps of different radii
for
interacting with the engaging member 215 carried by the end of the clevis 212
at the
bottom of the back rest frame 200, as will be seen more clearly in FIG. 16. In
the
preferred embodiment, the engagement member 215 is in the form of a nose-like
protrusion.
The outer edge 158 of stop plate 154 has specific steps 159, 160, and 161, as
can
be best seen in FIG. 28, and each is at a different distance from the central
axis defined
by aperture 157 with respect to the other. A locking means 163, in the form of
a spring-
biased plunger is mounted in a boss 164 on the bottom of seat plate 330 and
engages
detents 165, 166 and 167 found in the upper portion of stop plate 154. It will
be noted
that the outer edge 158 of stop plate 154 could be a smooth cam having an edge
of a
continuously changing radius. The number of detents determines the number of
fixed
chair back tilt positions.
The indexing detents 165, 166 and 167 are of concave shape and are adjacent
each other. Since the spring-loaded plunger is in the form of a spring-loaded
ball 163, the
plunger is enabled to freely move from one concave detent to another by
compressing
the spring and rotating the lever 156 and thus the stop plate 154 to permit
the plunger to
be positioned in any selected detent and by releasing the plunger to cause the
stop plate
to hold the back frame in a selected tilt position.
Because the projection 215 is below the pivot axis P20 formed at ends 120 and
210, as the back frame 200 pivots about axis P20, the protrusion 215 moves
inwardly
towards the seat stop plate 154 thus allowing adjustment of the tilt mechanism
by
moving handle or lever 155. The handle 155 is fixed from rotation relative to
stop plate
154 via a number of matching spring fingers 168, engaging recesses in the
handle. When
the lever 155 and the stop plate 154 rotate, it causes the various steps 159,
160 and 161
on the outer edge thereof to be in selective engagement with the projection
215. The
details of the tilt limit module are disclosed and claimed in U.S. Patent No.
6,616,231
"Multi-Position Tilt-Limiting Mechanism".
CA 02450042 2007-08-20
-I8-
Turning now to FIGS. 15, 16a, 16b and 17, the complete backrest assembly 200
of the chair 10 is illustrated in perspective and shows the novel feature of
the lumbar
support construction and carrier assembly which will be described in detail.
Yet another novel and highly functional feature of the chair 10 that offers
ergonomic advantages over the prior art is the construction of the chair back
20. As
previously noted, the back 20 is designed to include a panel of fabric mesh
290 which is
preferably of an open weave type known in the art. The construction of the
fabric mesh
290 may have a variety of weave configurations. One configuration that has
proved to be
advantageous is shown in FIG. 21 a comprising vertical strands 291 of
multifilament yarn
and horizontal monofilaments 292. The monofilaments 292 in this construction
can be
seen to cross over the strands 291 and also crisscross over each other thereby
locking the
strands 291 in place.
A preferred mesh weave is shown in front and back views in FIGS. 21 b and 21
c,
respectively. In this version, the horizontal multifilament or weft material
295 is simply
interwoven in steps with a vertical monofilament warp 296. In the illustrated
embodiment the warp does not cross the weft at each adjacent position. In this
pattern for
each warp cross over a weft, there will be seven warps between that do not
cross the
same weft before a repeat. Thus warps "0" and "8" cross weft C, while warps 1
and 9
cross weft D. The warp material preferably is made of Hytrel monofilament of
730
Denier. This provides structure and a relatively "shiny" look to the back of
the chair. The
weft 295 is a multifilament which includes a polymer yarn and an amount of
Hytrel .
The multifilament is a suitable synthetic resin and provides a relatively soft
and
comfortable feel to the front surface of the chair back. Because of the
pattern, it also has
a more finished and pleasing esthetic look as compared to open mesh of
different
patterns.
In order to support the mesh 290 around its edges, the aforementioned carrier
220
is used. The physical connection of the carrier 220 to the mesh 290 may be
performed in
a number of ways. However, a most reliable connection is disclosed in U. S.
Patent No.
6,511,562 entitled "Bonding Strip for Load Bearing Fabric". FIGS. 15, 20, 22
and 23
illustrate a carrier 220 comprising two halves 221 and 222 disposed on
opposite sides of
the edge portion of mesh 290. The two halves 221 and 222 may, in one form, be
formed
with internal grooves 224. The halves are placed in a fixture 225 together
with an
adhesive 226. The adhesive extends through warps and wefts of the fabric 290
and into
pockets formed by the grooves 224 and, once cured, creates a mechanical
CA 02450042 2003-12-08
WO 02/102199 PCT/US02/18787
-19-
interconnection that is of high strength and durability, and also helps hold
the two halves
221/222 of the carrier 200 together. Additional features (not shown) such as
screws or
the like also may be used to assure the parts to not separate. While halves
221, 222 are
shown as approximately equal size in the preferred form, as illustrated in
FIGS. 24 and
25, the one side is larger than the other, providing a more pleasing esthetic
look to the
mounted carrier.
The carrier 220 is formed as a generally rectangular semi-rigid meinber of
resilient, stretchable material. In order to support the carrier 220 with mesh
290, in
accordance with the invention and referring once again to FIGS. 2, 6, 20 and
16a and 24,
the main back fraine uprights 201 each has spherical end asseinblies portions
205 thereon
which are "snap fit" received witllin circular apertures 227 formed in the
upper right and
upper left hand corners of the carrier 220. These joints allow upper edge 231
of the
carrier 220 to flex allowing the chair back 20 to comfortably conform to the
position of
the user's shoulders. The back may be secured along bottom edge 232 to the
lower
transverse frame member 208 by a series of five outwardly depending tabs 238
formed
on the bottom of transverse member 208, which tabs fit into coinplementary
recesses 223
formed in lower surface 232. Details of the upper ball and socket connections
may be
seen in the cross-sectional view of FIG. 24, while the lower attachment
construction can
be seen in detail in FIG. 25. In assembly, the lower edge 232 is first
assembled to the
tabs, tension applied to the carrier 220 and the upper openings 227 snapped
into the
spherical ends 205 of uprights 201.
It can now be appreciated that a chair back construction as just described
offers
considerable ergonomic advantages. The use of open mesh 290 allows the chair
back 20
to not only breathe, but to flex in conformity with the back of the user. The
back 20 is
also highly cost effective to manufacture and assemble. Further, the back
member is
positioned on the frame assembly 200 in a manner that keeps the carrier and
mesh in
tension, providing both flexibility of the back surface but sufficient
rigidity for the
carrier that it maintains its shape. Because the lower transverse member 208
is curved
and set forward of the uprights 201 (via C members 209), the lower end 232 of
the
carrier assuines a curved configuration that also is spaced forwardly of the
uprights 201,
so the user never feels the back frame.
As observed the carrier 220 has a slight curvilinear shape from top to bottom
so
as to assume compressing tension in the mesh fabric. When a user's back
contacts the
fabric at various locations and during casual movement in the chair. The
curvilinear
CA 02450042 2007-08-20
-20-
shape also is intended to provide support in the general lumbar region, as
best seen in the
side view of FIGS. 4a and 4b.
Furthermore, a major advantage of this tensioned structure is the capability
to
provide a unique adjustable lumbar support. The back assembly 200 includes a
transverse lumbar support tube 250 having gripping means 251 on each of its
opposed
ends, together with a pair of spaced slide members 253. A cross-section of the
gripping
means 252 can be seen in FIG. 20 wherein the carrier 220 is provided with a
pair of
opposed recesses 254 into which opposed projections 255 of the gripping means
252 are
slidably received, with the carrier trapped between the projections 255. Thus,
the lumbar
support tube 251 is slideable on opposed edges of the carrier 220.
FIG. 18 illustrates a cross-sectional view of the support tube taken
substantially
along the line 18-18 of FIG. 15. There, it can be seen that slide members 253
are
configured to engage vertical supports 201. As shown in FIGS. 16b and 19, the
engagement arrangement of the slide members 253 includes simple vertical
grooves 256
formed in the supports 201 and engaging a central rib 257 on the slide member.
It can
now be appreciated, particularly with reference to FIG. 17, that the lumbar
support tube
251 is vertically movable between upper and lower positions as it slides on
edges of the
carrier 220 by means of the gripping means 252 and also slides on the vertical
supports
201 by means of the slide members 253. The result of such movement is to allow
the
chair user to adjust the vertical height of the lumbar support tube 251 by
simple manual
manipulation. The lumbar tube 251 is held in proper connection to the supports
201 by
the tension of the carrier 220 and mesh 290 without the need for screws,
adjustment
knobs or the like. In this tension mode the lumbar tube 251 causes the carrier
220 and
mesh 290 to be forced forwardly of the chair uprights in the lumbar region of
the user,
while direct contact of the lumbar support tube 251 with the back of the user
is avoided.
An in-depth description of this assembly may be found in aforementioned U.S.
Patent
No. 6,572,190.
The vertically adjustable lumbar support member 250 is intended to change the
lineal curvature of the carrier 220 as the tube 251 is slide up or down
between the carrier
220 and uprights 201. By changing the carrier configuration, no high pressure
contact
points are placed on the user's back; rather, a taut but flexible mesh is
properly
positioned for preferred support and comfort, even as the chair reclines.
Turning now to other aspects of a preferred seat 30 developed for use with the
ergonomic chair, various aspects of the horizontal seat adjustment and unique
cushion
CA 02450042 2003-12-08
WO 02/102199 PCT/US02/18787
-21-
arrangement will be described in detail with reference to FIGS. 29-31. The
seat plate
330 has been generally described heretofore. the plate 330 is intended to
cooperate with
a seat pan 301 which has the seat cusliion assembly 500 affixed thereto.
The seat pan 301 may be made of any suitable material such as a synthetic
resin
which may be molded as an integral piece. The seat pan 301 includes an upper
portion
304 and a lower portion 305. The upper portion is covered with a cushion
assembly 500
described hereinafter and forms the seating surface of the chair 10. The seat
pan also
includes four spaced L-shaped fingers, 306, 307, 308 and 309 depending from
the lower
portion 305, a fastener receiving opening 310, a rim 318 around the fastener
receiving
opeiiing and two abutinent elements 312, 313. The seat pan 301 also includes a
front
portion 314, and a rear portion 315. A large opening 316 is located in the
rear portion
315 of the seat pan to accommodate movement of the links 216. Peripheral
fastener
openings, such as the openings and bosses 317 are provided to fasten the seat
cushion
assembly 500 to the seat pad 301. The seat pan further includes a nuinber of
strengthening ribs such as the rib 318 in the upper portion. Flanking the
fastener
receiving opening 310 are two depending bumps 319, 320. The fastener receiving
opening 310 and the two bumps 319, 320 are formed on a beam 321. Because the
material of the seat pan 301 is a synthetic resin, the beam 321 is resilient
and thus able to
flex in response to any applied force. Such a force may come from the fastener
303
being received through the fastener receiving opening as well as from contact
with the
seat plate 330 which may provide forces on the two bumps 319, 320. The
abutment
elements 312, 313 are also formed at the end of respective beams 322, 323 for
added
flexibility.
The seat plate 330 may be formed as an integral unit of any suitable strong
material, such as aluminum. As noted, the seat plate includes a front portion
331, a rear
portion 333, a top portion 334 and a bottom portion 335. The seat plate
includes four
guide slots 336, 337, 338, 339, each with a large head opening and a narrow
body
opening (FIG. 29), which cooperate with the L-shaped fingers 306, 307, 308,
309,
respectively, of the seat pan 301 for restraining and guiding the seat pan 301
in
movement in a horizontal direction relative to the fixed seat plate 330.
The seat pan 301 also includes an elongated fastener receiving opening 340 and
two abutment limit slots 341, 342. These limit the horizontal movement of the
seat pan
by limiting the movement of the abutment elements 312 and 313. At the rear
portion of
the seat plate is a large opening 345 that receives the clevis 212 and links
216. On either
side of the elongated fastener receiving opening 340 is a set of recesses 336,
337 in the
CA 02450042 2007-08-20
-22-
top portion. The pair of sets of recesses form a detent with the pair of
depending bumps
319, 320 on the lower portion of the seat pan. The limit slots 341, 342
receive the
abutment elements 312, 313, respectively and limit movement of the seat pad so
that the
L-shaped fingers do not disengage from the guide slots. The torque limiting
fastener 303
is provided for seat adjustment. The design of the fastener 303 is such that
once inserted
it cannot easily be removed. Details of the fastener are disclosed in U.S.
Patent No.
6,634,711, entitled "Adjustable Chair Seat With Locking Mechanism", referenced
above.
In operation the seat pan 301, seat plate 330 and fastener 303 are all formed
using
well known techniques. Assembly is simple and easy. The seat pan 301 and the
seat plate
330 are aligned to allow the L-shaped fingers 306-309 to pass through the
enlarged
openings at the end of the guide slots 336-339 and for the abutment elements
312, 313 to
be pressed into the limit slots 341, 342. Thereafter, the fastener 303 is
threaded into the
fastener receiving opening 310 of the seat pan 301 with the seat plate 330
sandwiched
between. Once the seat pad and the fastener are engaged, they will not
separate;
however, the fastener 303 may be loosened or tightened simply by rotating the
handle
clockwise or counterclockwise. When the fastener is loosened, the seat pan may
be
adjusted generally horizontally relative to the seat plate for the user's
comfort. Because
of the bumps 319, 320 and recesses 336, 337, a detent is formed which is
easily heard
and felt by the chair user and this helps in the adjustment process. When the
adjustment
is complete, the fastener is counter rotated to squeeze the seat pan and the
seat plate
together.
Another improvement in the ergonomic chair is a highly effective seat cushion
assembly.
FIG. 32 is an exploded view of one embodiment of a seat cushion assembly 500
preferred for use with the chair 10 of the present invention. Seat cushion
assembly 500
comprises foam body 512 which can be formed of materials typically used in
such seat
cushions, such as open-celled or closed-celled polyurethane foam. The foam
body 512
has an upper surface 513 and a plurality of vertical columns 515 disposed
substantially
centrally in the foam body 512. In the illustrated embodiment, the columns 515
extend
upwardly such that the top surface of the columns 515 define a curved surface
substantially parallel to upper surface 513. In the embodiment illustrated in
FIG. 32, the
columns 515 are formed integrally with foam body 512. The foam material of
which
foam body 512 and columns 515 are made will be resiliently deformable to some
extent.
The columns 515 are structured such that, in the absence of other structural
elements of
CA 02450042 2003-12-08
WO 02/102199 PCT/US02/18787
- 23 -
the asseinbly 500, each coh.unn 515 is capable of deflecting substantially
independently
of the other colunuis 515 in response to compressive forces applied by a chair
user.
The vertical columns 575 are structured so as to define a plurality of air
spaces
516 therebetween, which together define a plenum or air reservoir 518. A
plurality of
channels 520 is disposed within foam body 512 and extend from air reservoir
518 toward
the periphery of foam body 512. In the illustrated preferred embodiment of a
seat
cushion, the channels 520 are directed to the front and lateral sides of the
foam body 512.
Design parameters of vertical columns 515 include their number, planar
spacing,
depth, aspect ratios, and material density and stiffness. Depending on their
size and
shape, the number of vertical columns is preferably about 40-80. The columns
preferably can have a diameter at their lower end in the range of about 1.0-
2.0 inches.
The columns can have a diameter at their upper end in the range of about 0.9-
2.0 inches.
The height of the columns can range up to about 4 inches, and most preferably
will be in
the range of about 0.5-1.5 inches. The columns 515 in the seat cushion 512 can
be of
different sizes and shapes. The number of air channels 520 will depend upon
their size.
The total volume capacity of channels 520 will be a function of the volume
capacity of
air reservoir 518.
The seat cushion assembly 500 further comprises an elastomeric layer 530 that
overlays the upwardly extending columns or risers 515. In the illustrated
embodiment,
the periphery 531 of elastomeric layer 530 is seated within a fitting edge 514
at the upper
surface 513 of foain body 512. Elastomeric layer 530 comprises a top surface
532 and a
bottom surface 534. The bottom surface 534 of elastomeric layer 530 defines
the top
surface of air reservoir 518. The elastomeric layer 530 comprises a material
having
significant resilience and flow properties. Suitable materials for elastomeric
layer 530
include, for example, a gelatinous sheet and a polymeric membrane, or other
gelatinous
materials with variable viscoelastic properties. One suitable material
includes a gel sold
under the trademark LEVAGEL by Royal Medica of Italy. Information about this
material is available at www.royalmedica.it. The elastomeric layer 530 and
upwardly
extending risers or columns 515 are each characterized by both an elastic
stiffness value
and a dissipative stiffiiess value In a preferred embodiment of the invention,
the ratio of
elastic stiffness to dissipative stiffiiess of the vertical columns 515 is
greater than the
ratio of elastic stiffness to dissipative stiffness of the elastomeric layer
530.
Depending on the material selected and the properties of the seat cushion
desired,
elastomeric layer 530 can have a thickness in the preferred range of about 0.2-
0.4 inches.
CA 02450042 2003-12-08
WO 02/102199 PCT/US02/18787
-24-
The area of elastoineric layer 530 can be less than the area of top surface
513 and most
preferably in the range of about 30-55%. In one embodiment, elastomeric layer
530 is
about 0.25 inches thick, and has an area of 210 sq. in., relative to a total
area of top
surface 513 of 392 sq. in.
In use, the foam body 512 of seat cushion assembly 500 is supported by a stiff
seat pan 301 rigidly fixed on the seating system assernbly 300. The seat pan
301
comprises an inner pan 526 fastened to the seat pan 301.
When a user is seated on a seat cushion of the instant invention, the user's
weight
is transmitted as vertical compressive forces and transverse shear forces to
the user/seat
cushion interface. These forces are transmitted through elastomeric layer 530
to vertical
columns 515. Elastomeric layer 530 and vertical columns 515 function
cooperatively
with one another to achieve a self-limiting mechanical response to obtain
desired
mechanical qualities.
The redistribution of applied forces can be further enhanced by an air-
permeable
layer 535, disposed above elastomeric layer 530. The air-permeable layer 535
may
coinprise an open-cell or non-woven viscoelastic material having specified
thickness and
viscoelastic properties, which air-permeable layer 535 can function to further
dissipate
applied forces before such forces reach elastomeric layer 530. Optionally, an
intermediate foam layer 531 can be placed between air-perineable layer 535 and
elastomeric layer 530. A cover fabric, not shown, can overlie the entire
seating structure.
The layers 512, 530, 535, and the cover fabric can be pre-bonded to one
another such as
with adhesives. Alternatively, the layers can simply be stacked on top of each
other, in
which case there should be a sufficient amount of friction between the layers
to prevent
slippage of the layers with respect to one another in response to shear forces
applied
during use.
The structure of the instant invention will transmit shear forces emanating at
the
user/seat interface across the interfaces between each of the layers until
elastomeric layer
530. Elastomeric layer 530 will deform viscously in response to applied shear
forces,
thereby counteracting the shear component of the user's weight by dissipative
means,
such that the user's skin will not experience the shear component. As a
result, the user's
tissues will experience substantially only compressive stresses in the normal
direction.
This reduction in shear stress can reduce the potential for the development of
pressure
ulcers, and reduce undesirable interference with blood vessel activity in the
vicinity of
these tissues. Moreover, the unique arrangement and air pressure helps to
avoid heat
CA 02450042 2007-08-20
-25-
build-up which frequently occurs in chairs and has an advantage over mesh
seats which
may feel cool and drafty.
When the user leaves the seat cushion of the instant invention, the resiliency
of
the foam body 512, vertical columns 515 and the elastomeric layer 530 allows
full
recovery of both shear and compression deformational mechanisms of the
cushion. The
passive air pump depressurizes, allowing outside air to pass through the
outside cover,
the air permeable layer, and optional intermediate foam layer to enter the air
reservoir
and channels, and open cells in the foam body 512 if open-celled foam is used.
The
elastomeric layer 530 will also return to its original shape prior to the
application of
compression and shear forces by a user.
The preferred seat cushion assembly and the advantages thereof are more
particularly described in U.S. Patent No. 6,598,251, entitled "Locking Device
for Chair
Seat Horizontal Adjustment Mechanism".
As previously noted, another aspect of the improved ergonomic chair includes
improved arm assemblies 40 that are both vertically adjustable and in which
the armrests
408 are rotatable generally in a horizontal plane.
The disclosure herein concentrates on the armrest assemblies which are simply
constructed and reliable and allow adjustment both vertically and
horizontally. Referring
now to FIGS. 33-37, the armrest assembly 40 includes an upstanding support 400
which
has an open upper end portion 401, a curved lower end portion 402 and a
longitudinally
extending opening 403 extending downwardly from the upper end portion. Within
the
support opening 403 are mounted oppositely disposed liner racks 404, 405, each
having a
plurality of notches extending in a longitudinal direction. As viewed in FIG.
34, the
longitudinal direction is generally vertical.
A guide tube 407 is positioned in the support opening 403 such that the guide
tube is generally vertically movable relative to the support. An armrest 408
is mounted to
the guide tube so that relative movement of the guide tube causes vertical
adjustment of
the armrest.
Within the movable guide tube is an elongated element 409 in the form of a
rod,
the rod being mounted within the guide tube to be rotatable only. As will be
explained
below, the rod 409 does not slide vertically or longitudinally relative to the
guide tube
407. Mounted to the elongated rod 409 is a locking element 410 which is
rotatable with
CA 02450042 2003-12-08
WO 02/102199 PCT/US02/18787
-26-
the rod to selectively engage and disengage the opposed notches 406 of the
liner racks
405, 405. Mounted at an upper end portion 411 of the rod is an activator nut
412 which
engages the rod and causes the rod to rotate, the engagement surface of the
nut moving
between raised and lowered positions (raised in FIG. 35). A spring 413 is
mounted
between the activator nut and the guide tube and biases the activator nut to
the raised
position whereby the rod is rotated to and maintained in a locked position.
The activator
nut is moved by a lever 414 which is operatively connected to the upstanding
support by
being pivotally mounted to an armrest base 415. A cap 416 is also mounted to
the guide
tube and is operatively connected to the armrest base to allow the base to
rotate in a
generally horizontal direction relative to the cap.
The upstanding support 400 has a generally cylindrical shape extending in a
generally vertical direction. The lower end portion 402 of the upstanding
support curves
to a generally horizontal disposition allowing it to be attached to the
central base member
100 of the chair 10. The support is made of any suitable material, such as
aluminum.
Fonned around the upstanding support is a second cylindrical element 417 often
referred to as a shroud. The shroud slides along the outside surface of the
upstanding
support and provides a pleasing aesthetic appearance to the armrest assembly.
An upper
part 418 of the shroud 417 includes a first horizontal annular bearing surface
419, a
vertical annular bearing surface 420 and a second horizontal annular bearing
surface 421.
These bearing surfaces engage corresponding bearing surfaces of the armrest
base 415.
The shroud also includes a top flange 422 having fastener receiving openings
423, 424.
As mentioned, within the upstanding support 400 are the two oppositely
disposed
liner racks 404, 405, with each rack including the plurality of notches 406.
The racks
have small tabs 425, 426 wliich engage openings 427, 428 in the upstanding
support. In
addition to the notches, the racks also include bearing surfaces 429, 430 for
the vertically
sliding guide tube 407.
The guide tube is generally cylindrical in shape and includes a central
opening
431, FIG. 36-40. The guide tube includes an upper end portion 432 including
two
fastener openings 433, 434, an annular groove 435 for receiving the spring 413
and two
oppositely disposed keys 436, 437. Along an outside surface 438 of the guide
tube are
grooves, such as the grooves 439, 440, for limiting the upward travel of the
guide tube.
Toward a lower portion 441 of the guide tube, there are two circumferentially
extending
slots 442, 443. The slots each extend about an arc of about forty-five
degrees. As will
be explained below, the locking element 410 extends through the slots to make
CA 02450042 2003-12-08
WO 02/102199 PCT/US02/18787
-27-
engagement with the notches 406. When engagement is made, the guide tube 407
and
the attached armrest 408 are locked relative to the support 400. The slots
442, 443 also
enable the locking element to rotate out of engagement with the notches
through the
forty-five degree arcs and thereby disengage the guide tube from the support
allowing
the guide tube to be moved vertically within the support opening 403. In this
manner the
armrest may be vertically adjusted.
tMounted to the guide tube 407 is the activator nut 412, FIGS. 33, 34, 36, 38
and
40. The activator nut includes an annular flange 444, having a spring
retaining surface
445 and key slots, of which one key slot 446 is shown in FIG. 10, to
accominodate the
keys 436, 437 of the guide tube. The actuator nut also includes a top surface
447 to
engage the lever 414 and a central threaded opening 448. The threaded opening
engages
the rod 409 causing the rod to rotate.
Mounted within the guide tube is the elongated rod 409, FIGS. 38, 39 and 41.
The rod is mounted for rotational movement only and does not slide
longitudinally in
relation to the guide tube. At an upper end portion 411 of the rod is an
external screw
thread 449 which engages the internal screw thread 448 of the activator nut.
In the lower
portion of the rod is a snap fit connector 450 for engaging the locking
element 410. The
locking element has opposed extending arms 451, 452 and a central opening 453.
The
locking element central opening receives the snap fit connector of the rod,
which
deforms and then snaps back into place to make a connection.
The spring 413 is mounted within the arulular groove 435 at the upper end
portion 432 of the guide tube 407. An upper end of the spring bears against
the surface
445 of the annular flange 444. Because of the keys and key slots, the
activator nut
moves between raised and lowered positions in a linear fashion as shown in
FIG. 35.
When the activator nut is moved to its lowered position, the spring is
compressed and
forms a biasing force against the activator nut tending to return it to its
raised position.
Referring now to FIGS. 42-44, the armrest base 415 is shown in more detail.
The
base is an integral element having a large oval opening 454 at an extended end
portion to
accommodate a touch pad 455, FIGS. 33 and 48, of the operating lever 414. At
the
opposite end of the armrest base is a cuplike structure including a bottom
bearing surface
456 and a downward projecting flange 457 forming a vertical bearing surface
458 for
rotation about the shroud. The armrest base also includes a cup upper surface
459. The
upper surface 459 includes two sets of recesses 460, 461, each in a curved
format. These
recesses form a detent with the cap 416 as will be explained below. The cup
bottom also
CA 02450042 2003-12-08
WO 02/102199 PCT/US02/18787
- 28 -
includes an opening having a central portion 462 and two end portions 463,
464. The
end portions are curved slots to accommodate two fasteners 465, 466, FIG. 4,
allowing
the base to pivot until the ends of the slots abut the fasteners. The central
portion 462
allows the lever to engage the top surface 447 of the activator nut 412.
The cap 416 includes two side openings 467, 468, FIGS. 45-47, for receiving
the
fasteners 465, 466 and a central opening 469 for passing the lever. The side
openings are
aligned with the end portion slots 463, 464. The cap also includes two sets of
resiliently
mounted tabs 470, 471. The tabs align with and engage the two sets of curved
recesses
460, 461 on the armrest base to form a series of detents. This allows
horizontal
movement of the armrest base from one detent to another within about a forty-
five
degree arc determined by the arcs of the end portion slots 463, 464 and
depending
shoulders 472, 473 surrounding each opening 467, 468, respectively.
Mounted to the armrest base 415 is the lever 414 which extends from the oval
opening 454 at one end of the armrest base to the central opening 462 at the
other end
portion of the armrest base. At the extended end of the lever is the touch pad
455, FIG.
48, while at the other end is a depending projection 474, FIGS. 35 and 48,
that makes
contact with the upper surface 447 of the activator nut 412. The lever is
mounted to
pivot about pivot point 475 such that an upward force on the touch pad 455
causes the
projection 474 to move downwardly. The downward movement of the lever
projection
causes the activator nut to move from its raised position to its lowered
position thereby
causing the rod 409 to rotate and disengage the locking element 410 from the
notches
406.
Referring now to FIGS. 49 and 50, the pivoting movement of the locking element
410 is clearly shown. In FIG. 49 the armrest is locked with the locking
element
engaging the notches 406. When the lever is activated, the locking element is
pivoted
out of engagement with the notches as shown in FIG. 50.
It ca.n now be appreciated that the armrest assembly is simply constructed,
easy to
form and assemble and easy to use. In operation, the relative vertical
positioning of the
armrest, the guide tube and the connected shroud to the upstanding support and
the
notched liner racks determines the height of the armrest relative to the seat
of the chair.
Usually the armrest is locked by the locking element engaging a pair of
notches.
Depressing the lever touch pad causes the projection end to bear down on the
top surface
of the activator nut. Since the nut cannot rotate, it is depressed causing the
threadedly
engaged rod to rotate. Rotation of the rod causes the locking element to
rotate 45
CA 02450042 2003-12-08
WO 02/102199 PCT/US02/18787
-29-
degrees out of engagement with the pair of notches. The armrest may then be
manually
adjusted upwardly or downwardly. Once the force on the lever is released, the
spring
mounted to the guide tube causes the actuator nut to return to its raised
position. This
linear movement of the activator nut causes reverse rotation of the rod and
the locking
element causing the locking element to engage a new pair of notches. When this
occurs,
the armrest is locked in its new position.
Adjusting the armrest in a horizontal direction requires only the movement of
the
armrest to pivot it outwardly or inwardly within an arc of about 45 degrees.
The
resiliently mounted tabs of the cap move from one pair of recesses to another
pair in the
armrest base. This detent mechanism allows the armrest to pivot between six
discreet
positions. Movement occurs when the force on the armrest is sufficient to move
the
resilient tabs out of engagement with a pair of recesses.
What has been described is a simply constructed and reliable armrest assembly
that is adjustable both vertically and horizontally. These adjustments may be
easily
made through simple manipulation of portions of the armrest assembly.
Referring now to the drawings, and initially to FIGS. 51, 52 and 53, another
ergonomic chair constructed in accordance with the numerous principles of the
invention
is shown in front perspective and designated generally by the reference
numeral 610.
The chair 610 comprises as its principal components a seat 612 and back 614.
Suitable
arms 616 having upper pads 618 may be provided. The chair 610, in a
conventional
manner, may be supported on a spider base 620 movable on casters 622.
As shown in FIGS. 54-60, the chair 610 is so constructed as to have
synchronous
movement of the seat 612 and back 614. To this end, a pair of main seat and
back
supports 624 are rigidly attached to a central support module 625 having a hub
626 for
frictionally receiving the upper end of a gas cylinder 628. The gas cylinder
628 is
preferably a two-stage type available from Stablis GmbH of Germany. This
cylinder 628
is operable by a manually pivotable lever 630 which activates the cylinder 628
for height
and adjustability of the chair 610 in a manner well-known in the art. The
chair arms 616
are rigidly connected to the supports 624. A seat pan 632 is pivotably
connected at its
front end to the forward end of the supports 624. A back frame assembly 634 is
also
pivotably connected to the upper rear of the supports 624. The chair back 614
in the
preferred embodiment is of fabric mesh 636 construction supported around its
periphery
by a carrier 638. An adjustable lumbar support member 640 slidably connects to
the
carrier 638 and bears against the back frame assembly 634.
CA 02450042 2003-12-08
WO 02/102199 PCT/US02/18787
-30-
The relative positions of the seat 612 and back 614 of the chair 610, during
reclining of the back 614, can be seen in the side views of FIGS. 62-65. As
illustrated in
these views, the chair seat pan 632 is pivotably connected at pivot points P12
to the
supports 624 (only one of which can be seen) and is pivotably connected at
rear pivot
points P32 to a pair of links 642 (only one of which can be seen). Each link
642 in turn is
pivotably connected at point P34 to forward extensions of the back frame
assembly 634.
The back frame asseinbly 634 is also pivotably connected at point P14 to the
two supports
624. As shown in the dimensional schematic of FIG. 63, when the chair back 614
is in a
fully upright position the seat pan 632 in one preferred form is inclined to
the rear and
forms an angle of about 15.7 degrees from horizontal although this angle can
be in a
range of between about 10 and 20 degrees. The distance between pivot points
P12 and
P32 is about 12.889 inches and the distance between pivot points P32 and P34
of the links
642 is approximately 2.01 inches although these distances can be in ranges of
between
about 10 and 15 inches and about 1.5 to 2.5 inches, respectively. Further, the
distance
between pivot points P14 and P34 is approximately 4.71 inches while the
horizontal
distance between pivot points P12 and P14 is about 14.5 inches. The distance
between
pivot points P41 and P34 may be in the range of between about 3 and 6 inches
while the
distance between pivot points P12 and P14 may be in a range of between about
12 and 17
inches. As shown in the three stages of back tilt illustrated in FIGS. 62-65,
as the back
614 reclines rearwardly, the link 642 moves in a counterclockwise direction of
rotation
causing the rear of the seat pan 632 to elevate relative to its front. In the
fully reclined
position of the back 614 as shown in the schematic of FIG. 66 the seat pan
preferably
reduces its angle of inclination with horizontal from 15.7 degrees (FIG. 63)
to 8.7
degrees while the afore-described distances between all pivot points remains
constant.
The reduced inclination angle may be in a range of between about 6 and 10
degrees.
This synchronous motion of the seat pan 632 and back 614 provides for an
exceptionally
comfortable reclining motion of the chair 610 user to aid in avoiding fatigue
as the user
is performing various work-related tasks.
Shown now in FIGS. 67 and 68 are schematic views of the synchronous seat and
back tilt feature employing a four-bar mechanism which allows the rear of the
seat to
elevate as the backrest is reclined. The mechanism is designed to iinmediately
respond
to a user exerting a back force and/or self-weight on the seat. This function
allows for
reclining of the chair 610 about a rotation point C that is very closely
coincident with the
pivot axis of the user's hips and avoids undesirable "shirt pull" of the user.
Because the
rear of the seat is elevated during back reclining, excess pressure is
relieved at the front
underside of the user's thighs, and also a relatively constant gaze angle is
maintained
CA 02450042 2003-12-08
WO 02/102199 PCT/US02/18787
-31 -
during reclining. This provides for adequate fluid circulation in the user's
legs and
avoids swelling. To accomplish the foregoing advantages, the chair 610
comprises four
basic members and four rotationally-free pivots. The basic members include a
floor
supported member 660, a seat rest 662, a linking member 664 and a backrest
666. The
floor supported meinber 660 has an upwardly directed portion 668 that
terminates at an
end defining pivot point P12 to which the seat rest 662 is pivotably connected
at its
forward portion. The member 660 also has an upwardly directed portion 670
which
terminates at an end defining pivot point P14 to which the backrest 66 is
pivotably
connected. A lower portion 672 of the back rest 666 is pivotably connected at
point P34
to the linking member 664 and a downwardly extending portion 674 of the seat
rest 662
is pivotably connected at point P32 to the other end of the linking member
664.
The kinematics of the chair 610 are illustrated in FIG. 68. As force F is
applied
on the backrest 666, the back tilt angle (3 increases, eye location shifts
backwards an
amount AH1, and eye elevation decreases by an amount AV3. The change in back
tilt
angle (3 transmits motion by way of the upper and lower back pivots P14 and
P34,
respectively, to the linking member 664. As a result of motion set in linking
member
664, the rear seat pivot P32 moves in coordination with pivot P34 in a
composite rotational
and translation motion. As the seat rest 662 rotates about pivot P12, a lift
AV2 is caused
in the rear part of the seat rest 662 relative to its front edge M in the
amount AV2-dVl,
therefore introducing a seat rest angle a. The user sitting in the chair will
feel a weight
reduction effect as a result of the lift. The apparent weight reduction will
be sensed as
lightness and give the feel of comfort.
In order to assist the chair linkage mechanism in allowing the back 614 to
maintain a fully upright positioil wheii the chair 610 is not in use, as shown
in FIG. 61
one or more extension springs 680 may be connected between pivot shaft 682 and
a rear
edge portion 684 of the seat pan 632. The pivot shaft essentially defines
pivot points P34
and will cause a return force to be exerted on back frame assembly 634 by the
springs
680.
It can now be appreciated that the chairs 10 and 610 constructed according to
the
invention offers considerable advantages in user comfort by virtue of their
synchronous
linkage construction particularly where it is used for prolonged periods of
time. The
chairs are also cost effective to manufacture and assemble.
While the present invention has been described in connection with a preferred
embodiment, it will be apparent to those skilled in the art that many changes
and
CA 02450042 2003-12-08
WO 02/102199 PCT/US02/18787
-32-
modifications may be made without departing from the true spirit and scope of
the
present invention. Accordingly, it is intended by the appended claims to cover
all such
changes and modifications as come within the spirit a.nd scope of the
invention.
